Semiconductor package with a controlled impedance bus and method of forming same

ABSTRACT

An apparatus includes a first substrate having a set of semiconductor devices formed within it. The apparatus also includes a second substrate. A third substrate has a data conductor coupled between first and second connections to the second substrate. The data conductor is coupled to the set of semiconductor devices at respective connection points.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of prior U.S. patent application Ser.No. 09/471,305, filed Dec. 23, 1999, which application is incorporatedherein in its entirety now U.S. Pat. No. 6,404,660.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to the physical layout of semiconductorsystems. More particularly, this invention relates to a high densityplanar semiconductor system with a controlled impedance co-planarinterconnect channel.

BACKGROUND OF THE INVENTION

Semiconductor systems are implemented in a variety of configurations.One type of semiconductor system is a master-slave system in which asemiconductor-based master device controls a set of semiconductor-basedslave devices. An example of a master-slave system is a memory system inwhich a master device memory controller coordinates the operation of aset of slave devices in the form of memory modules. By way of example,the invention is described in the context of a memory system, althoughthe invention is equally applicable to other types of semiconductorsystems.

As computer processors increase in speed, there is a growing burdenbeing placed upon memory systems that provide data to computerprocessors. For example, video and three-dimensional image processingplaces a large burden on a computer memory subsystem.

One or more high frequency buses are typically employed to provide therequired bandwidth in such systems. The higher the frequency ofoperation of the bus, the greater the requirement that the signals onthe bus have high-fidelity and equal propagation times to the devicesmaking up the subsystem. High-fidelity signals are signals having littleor no ringing, and which have controlled and steady rising and fallingedge rates.

Many obstacles are encountered in assuring the uniform arrival times ofhigh-fidelity signals to devices on the bus. One issue is whether thebus is routed in a straight line or routed with turns. Turns of thelines may not permit the construetion of the bus lines in a waynecessary to achieve uniform arrival times of high-fidelity signals todevices on the bus.

The assignee of the present invention has filed a patent applicationentitled “High Frequency Bus System”, Ser. No. 08/938,084, filed Sep.26, 1997, the contents of which are expressly incorporated herein. Theforegoing patent application discloses a digital system 20 of the typeshown in FIG. 1. The system 20 includes a mother board 22, whichsupports a master device 24 and a set of slave modules 26A, 26B, and26C. A bus 28 is routed in a horizontal and vertical manner tointerconnect the master device 24 with the set of slave modules 26A,26B, and 26C, as shown in FIG. 1. The bus 28 is terminated in a resistor30.

FIG. 2 is a side view of one of the modules 26 of FIG. 1. Module 26 hasa set of slave devices 32A-32E mounted thereon. The slave devices 32 maybe mounted on one side or both sides of the module. The module alsoincludes a set of edge fingers 34 for coupling to the bus 28.

FIG. 3 is a top view of one of the modules 26 of FIG. 1. Module 26 has aset of slave devices 32A-32E mounted on it. Module leads 36 link the setof slave devices 32A-32E and thereby form a portion of the bus 28. Eachslave device of FIG. 3 is enclosed in it's own package 33A-33E.

The structure of FIGS. 1-3 represents state-of-the-art packaging formasterslave systems, such as memory subsystems, which are operated witha memory controller (master) and a set of random access memories(slaves). Each slave device of FIG. 2 is enclosed in its own package.Metal traces or module leads 36 are used between the packages.

Placing each slave device in its own package is relatively expensive.Furthermore, such an approach is relatively space-intensive. Inaddition, such an approach can result in substantive signal propagationdelays between, for example, the first and last slave devices in a rowof slave devices.

It would be highly desirable to improve the performance of semiconductorsystems, such as master-slave systems in the form of memory systems.Such improvements could be exploited to support the increasedinformation bandwidth of modem computers.

SUMMARY OF THE INVENTION

One embodiment of the invention defines an apparatus. The apparatusincludes a first substrate having a set of semiconductor devices formedwithin it. The apparatus also includes a second substrate. A thirdsubstrate has a data conductor coupled between first and secondconnections to the second substrate. The data conductor is coupled tothe set of semiconductor devices at respective connection points.

Another embodiment of the invention is a semiconductor system with aninterconnect channel with an input end to receive a set of input signalsand an output end to route a set of output signals. A set ofsemiconductor devices are formed in a substrate, with each semiconductordevice of the set of semiconductor devices being designed forindependent operability and being electrically isolated within thesubstrate from adjacent semiconductor devices of the set ofsemiconductor devices. Each semiconductor device includes a set of inputnodes and a set of output nodes formed on the surface of the substrate.The interconnect channel is positioned on the input nodes and the outputnodes of each semiconductor device of the set of semiconductor devices.The set of input signals from the input end of the interconnect channelis applied to each semiconductor device of the set of semiconductordevices to produce the output signals at the output end of theinterconnect channel.

The method of the invention includes the step of forming a set ofsemiconductor devices in a wafer. Each semiconductor device of the setof semiconductor devices is designed for independent operability and iselectrically isolated within the substrate from adjacent semiconductordevices of the set of semiconductor devices. The forming step alsoincludes the step of forming within each semiconductor device, a set ofinput nodes and a set of output nodes on the surface of the substrate.Faulty semiconductor devices and operable semiconductor devices are thenidentified within the set of semiconductor devices. A set of operablesemiconductor devices that are adjacent to one another on the wafer aresubsequently grouped. An interconnect channel is then applied to the setof operable semiconductor devices so as to electrically link input nodesand output nodes of each semiconductor device within the set of operablesemiconductor devices.

The interconnect channel may be a set of metal traces positioned overthe set of memory devices. Alternately, the interconnect channel may beformed on an interconnect substrate, such as a thin-film substrate,flexible tape, or a printed circuit board. The set of memory devices andthe interconnect channel may be positioned in a single package.

The invention improves performance in semiconductor systems, such asmaster-slave memory systems. The improved performance increasesinformation bandwidth of computer and computer subsystems. The inventionproduces high density systems with reduced signal propagation times. Thehigh density systems of the invention reduce packaging costs and improvethermal performance.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference should be made tothe following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a master-slave digital system constructed inaccordance with the prior art.

FIG. 2 illustrates a side view of a slave module from the master-slavedigital system of FIG. 1.

FIG. 3 illustrates a top view of a slave module from the master-slavedigital system of FIG. 1.

FIG. 4 illustrates a wafer with different sets of slave devices that maybe packaged in accordance with the invention.

FIG. 5 illustrates a wafer with uniform sets of slave devices that maybe packaged in accordance with the invention.

FIGS. 6A and 6B illustrate high density planar semiconductor systemswith co-planar interconnect channels in the form of metal traces inaccordance with embodiments of the invention.

FIGS. 7A and 7B illustrate high density planar semiconductor systems ofthe invention incorporated into a system of the type shown in FIGS. 1-3.

FIG. 8 illustrates buffering devices that may be used in accordance withan embodiment of the invention.

FIG. 9 illustrates a high density planar semiconductor system of theinvention connected to a motherboard in accordance with an embodiment ofthe invention.

FIG. 10 illustrates a high density planar slave device system with aco-planar interconnect channel in the form of a thin-film in accordancewith an embodiment of the invention.

FIG. 11 illustrates a high density planar slave device system with aco-planar interconnect channel positioned in a package, in accordancewith an embodiment of the invention.

FIG. 12 illustrates a high density planar slave device system with aco-planar interconnect channel implemented with a thin film and bondballs, in accordance with an embodiment of the invention.

FIG. 13 illustrates a high density planar slave device system with aco-planar interconnect channel implemented to isolate individualnon-functional slave devices.

FIG. 14 is an enlarged view of a portion of the device of FIG. 13.

FIG. 15 illustrates a wafer with different sets of slave devicesseparated by scribe lines.

FIG. 16 illustrates processing steps for grouping, cutting, andpackaging semiconductor systems in accordance with an embodiment of theinvention.

FIG. 17 illustrates a wafer with designated faulty dice identified inaccordance with the process of FIG. 16.

FIG. 18 illustrates a wafer with grouped, functional dice identified inaccordance with the process of FIG. 16.

FIG. 19 illustrates a wafer with interconnect channels positioned ongrouped, functional dice identified in accordance with the process ofFIG. 16.

FIGS. 20A-20C illustrates the formation, from a wafer, of a setsemiconductor systems with controlled impedance buses in accordance withan embodiment of the invention.

FIG. 21 is a cross-sectional view of an embodiment of the invention.

FIG. 22 is a cross-sectional view of a prior art system. Like referencenumerals refer to corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 4 illustrates a wafer 40 used to fabricate a set of semiconductordevices 41. Each semiconductor device 41 is designed for independentoperability and is electrically isolated within the wafer 40 fromadjacent semiconductor devices 41. Thus, as used herein, the term“semiconductor device” or “integrated circuit” or “die” refers to acircuit with active components and connecting wires formed in asemiconductor material, which also forms a perimeter border withoutactive components or connecting wires. The perimeter border withoutactive components or connecting wires associated with each semiconductordevice is referred to as a “scribe lane”. Typically, a semiconductordevice is cut along a set of scribe lines within a corresponding set ofscribe lanes to separate the semiconductor device from the othersemiconductor devices of a wafer. FIG. 4 illustrates scribe lanes 39surrounding each semiconductor device 41.

By way of example, each semiconductor device 41 may be a slave device,which may be a memory device, such as a DRAM or a SRAM. In the priorart, the wafer 40 is cut such that each slave device 41 is packagedseparately. In accordance with the invention, groups 42 of slave devices41 are positioned in a single package. As discussed below, the groups 42of slave devices 41 are linked by an interconnect channel positioned ontop of the slave devices. This configuration produces a high densitysemiconductor system with reduced signal propagation times. Furthermore,the configuration reduces packaging costs and improves thermalperformance.

FIG. 4 illustrates groups 42 of varying size. FIG. 5 illustrates a waferwith groups 43 of slave devices of a uniform size, each including fourslave devices 41 and a signal repeater 44. Observe that each slavedevice 41 and signal repeater 44 is surrounded by a set of scribe lanes39.

FIG. 6A illustrates a group 43 of slave devices 41 of the type shown inFIG. 5. The group 43 comprises a set of slave devices 41A, 41B, 41C,41D, and a signal repeater 44. The signal repeater 44 includes a set oftransceivers 45. The set of slave devices 43 may be cut from a wafer 40,as shown in FIG. 5. FIG. 6A illustrates scribe lanes 39. Observe thatthe far left scribe lane, far right scribe lane, and horizontal scribelanes in the figure have been used to cut the group 43 of slave. devices41. The interior vertical scribe lanes 39 have not been used to seperateadjacent devices 41, but still exist between slave devices 41.

In accordance with the invention, an interconnect channel 54 ispositioned over the set of devices 41A, 41B, 41C, 41D, and 44. In thisembodiment of the invention, the interconnect channel 54 is implementedas a set of metal traces 56A, 56B, etc. The metal traces 56 may beformed on the wafer during the fabrication process. Alternately, theymay be formed after wafer processing by using chemical vapor depositionor other well known semiconductor processing techniques.

The metal traces 56 forming the interconnect channel 54 constitutecontrolled-impedance transmission lines. The interconnect channel 54 isapplied to a minimum of two slave devices, but may be routed over anentire wafer. Each slave device 41 includes a set of device bond pads orvias 58. The metal traces 56 electrically connect the device bond padsor vias 58 so that signals can be routed into the devices 41.

FIG. 6B also illustrates a group 43 of slave devices 41 A-4D and arepeater 44. The repeater 44 includes a set of transceivers 45 and atermination resistor R_(T). The figure also illustrates vias or bondpads 58 connecting to the individual devices 41 and 44. Perimeter bondpads 58 are used to establish an electrical connection with a substratebond pad 51 via bond wire 53. The substrate bond pad 51 is positioned onsubstrate 55.

FIG. 7A is a top view of a slave module 26 of the type shown in FIG. 3.However, in the embodiment of FIG. 7A, a high density group of slave 43is mounted on the module 26. The figure shows the bus 28 connected tointerconnect channel 54. The impedance of the interconnect channel 54 isconfigured to substantially match the impedance of the bus 28. That is,the impedance of the interconnect channel 54 matches the impedance ofthe bus 28 within plus or minus 30%. In one embodiment of the invention,the interconnect channel has individual metal traces, each with acontrolled impedance between 20 Ohms and 100 Ohms.

Observe in FIG. 7A that the bus 28 is connected to the module 26 at afirst device 41A and at the last device 41E. All other communication onthe module 26 is via the interconnect channel 54. More particularly,FIG. 7A illustrates that the bus 28 is routed from a bus segment 28Ainto the package 43 via a bus segment 28B. Next, the bus 28 is routedwith conductor 54 to sequentially coupled slave devices 41A-41E.Finally, the bus 28 is routed out of the package 43 with a bus-segment28C, after which it is routed on the motherboard 26. This forms atransmission line environment with stubs 58 having a delay shorter thanthe edge rate of the transmitted signals.

The configuration of FIG. 7A stands in contrast to the configuration ofFIG. 3, in which each slave device is in a separate package and moduleleads 36 formed on the module 26 are used to establish connectionsbetween slave devices. The prior art configuration of FIG. 3 results inincreased expense and prolonged propagation times compared to the systemof the present invention, as shown in FIG. 7A.

FIG. 7B illustrates the bus 28 connected to an interconnect channel 54.In particular, the bus 28 is connected to the interconnect channel 54via leads 59 of package 57. The interconnect channel 54 includes aninterconnect substrate 72 (e.g., a thin-film device, flexible tape,printed circuit board, and the like) with vias 58 extending toindividual devices 41A-41F. Device 41E includes a termination resistorR_(T), while device 41F includes a set of transceivers 45. The value ofthe termination resistor R_(T) is selected such that its impedancesubstantially matches the impedance of the bus 28. That is, the value ofthe termination resistor is selected such that its impedance is withinplus or minus 30% of the impedance of the bus 28.

FIG. 8 illustrates signal buffers that may be used in accordance with anembodiment of the invention. In particular, the figure illustrates ametal trace 56 of the interconnect channel 54 connected to theindividual slave devices 41A, 41B, 41C, and 41D. Each slave devicesincludes an input signal buffer 47 and an output signal buffer 48. Thesignal repeater 44 includes a set of repeater buffers 49 to driveincoming and outgoing signals.

FIG. 9 illustrates another embodiment of the invention. FIG. 9illustrates a set of slave devices 52A-52E. The slave devices 52A-52Eare connected to the interconnect channel 54 through vias 58.

FIG. 9 also illustrates connections between the semiconductor substrate50 that includes the slave devices 52A-52E and a motherboard 62. A setof input/output bond pads 60 are used to establish electrical links witha motherboard 62 via bondwires 64.

FIG. 10 illustrates an alternate embodiment of the invention in whichthe interconnect structure is implemented on an interconnect substrate72. The interconnect substrate may be a thin-film device (e.g.,polyimide), a flexible tape, a printed circuit board, or similarstructure. The second substrate may be formed in a separate, optimizedprocess and then be applied to the substrate 50.

In the embodiment of FIG. 10, the slave devices have perimeter bond pads70, while the interconnect substrate 72 has bond pads 74. Bond wires 76are used to link the bond pads on the respective surfaces.

FIG. 11 illustrates another embodiment of the invention. In FIG. 11, thesemiconductor substrate 50 is linked, via bond balls 84, to aninterconnect substrate 80 in the form of a printed circuit board. Thus,in the embodiment of FIG. 11, a flip-chip configuration is used. Theadvantages of a flip-chip configuration can therefore be exploited inconnection with the invention. These advantages include reduced packageinductance, compact packaging, and reduced manufacturing cost.

FIG. 11 further illustrates that the substrate 50 and the printedcircuit board 80 are positioned within a package 90. For example, thepackage may be a standard plastic pin grid array (PPGA) package.External pins 92 may be electrically connected to the printed circuitboard 80 using conventional internal traces (not shown).

FIG. 12 illustrates an alternate embodiment of the invention. Inparticular, FIG. 12 illustrates a substrate 50 with device bond pads 70.An interconnect substrate 72, implemented as thin-film, flexible tape,or the like, is positioned on the substrate 50. A channel (not shown) isembedded in the interconnect substrate 72. The interconnect substrate 72includes interconnect substrate bond pads 74. Bond wires 76 link thedevice bond pads 70 and the interconnect substrate bond pads 74.Further, the interconnect substrate 72 includes bond balls 84 forconnection to a printed circuit board or other substrate. The embodimentof FIG. 12 represents a hybrid package including bond wires andflip-chip functionality. This embodiment underscores how the features ofthe invention can be implemented into a variety of packagingconfigurations, thereby providing an engineer with many design options.

FIG. 13 illustrates a technique of isolating a flawed slave device in aset of slave devices constructed in accordance with the invention. Thefigure shows a set of slave devices 52A-52F. Through standard testing ofthe slave devices it is determined that slave device 52D is flawed.Thus, it must be isolated from the remaining functional devices.

The circuit of FIG. 13 includes a reset line 90, which is connected toeach slave device 52A-52F. The figure also illustrates an interconnectchannel 54, linking each slave device via a set of bond pads. Element 92on each slave device is a single large bond pad symbolizing a set ofsmall bond pads or vias.

Each slave device 52A-52F includes a scan-in pad 100 and a scan out pad102. Bond wires 76 are used to connect a scan out pad 102 to a scan inpad 100 of an adjacent device. For example, as shown in FIG. 13, a bondwire 76 is used to connect scan out pad 102A of slave device 52A to scanin pad 100B of slave device 52B.

In the case of a flawed slave device, such as slave device 52D in thisexample, a bond wire 76 is used to connect the scan in pad 100D to aground pad 108. The slave device 52D is configured such that it isdisabled when its scan in pad 100D is grounded. Notwithstanding theflawed and disabled slave device 52D, the remaining slave devices canoperate by connecting a bond wire between the scan out pad 102C and theinput bypass bond pad 104A. A lead 106 connects the input bypass bondpad 104A to the output bypass bond pad 104B. A bond wire 76 links theoutput bypass bond pad 104B to the scan in pad 100E of slave device 52E.This configuration accommodates a flaw in a slave device 52D in a set ofset of slave devices 52A-52F.

FIG. 14 is an enlarged view of a portion of the device of FIG. 13. Inparticular, FIG. 14 illustrates a portion of slave device 52D, includinga scan in pad 100D and a scan out pad 102D. An input buffer 120 ispreferably connected to the scan in pad 100D, while an output buffer 122is preferably connected to the scan out pad 102D. The figure also showsa lead 106 connected between an input bypass bond pad 104A and an outputbypass bond pad 104B. It is appreciable from FIG. 14 that the lead 106is used to reduce the bond wire length when the device 52A is bypassed.In other words, in the absence of this lead 106, a relatively long bondwire would have to be used to span an inoperative device. By way ofexample, a relatively long bond wire 126 is shown in phantom in FIG. 14.Such a bond wire is relatively difficult to implement, is susceptible todamage, and creates a relatively high impedance. The present inventionavoids this problem through the use of the bypass lead 106, which isaccessed through relatively short bond wires 76. The short bond wire 76Ais connected between a scan out pad 102C and the output bypass bond pad104A, while the short bond wire 76B is connected between the outputbypass bond pad 104B and the scan in pad 100E.

FIG. 15 illustrates a wafer 40 with different groups 42 of slave devices41 separated by scribe lanes 39, which are shown as bold lines. Interiorscribe lanes 38 also separate individual slave devices 41 within eachgroup 42, as shown with dashed lines. The interior scribe lanes 38 arerelatively narrow scribe lanes that will not be used for cutting thewafer 40. The interior scribe lanes 38 account for tolerance errors thatoccur during the step-and-repeat operation when masks are made. Theinterior scribe lanes 38 prevent adjacent die patterns from overlappingwith each other.

An interconnect channel 54 connects individual slave devices 41 within asingle group 42. Thus, for example, interconnect channel 54A connectsindividual slave devices 41A, 41 B, 41C, and 41D of group 42A.

In the prior art, scribe lanes 39 are placed around each individualdevice 41. In contrast, with the present invention, standard scribelanes 39 can be placed around a group 42 of devices 41, while relativelynarrow interior scribe lanes 38 can be placed between devices 41 withina group, since the interior scribe lanes 38 will not be used forcutting. Space must be allocated on the wafer 40 for the scribe lanes39. Observe that with the present invention the amount of space reservedfor scribe lanes 39 can be reduced. This reduction in scribe lane spaceresults in more chips per wafer, thus reducing cost and improvingproduction capacity.

The novel structure of the invention facilitates new processes fortesting, cutting, and packaging semiconductor devices. FIG. 16illustrates a testing, cutting, and packaging process 140 utilized inaccordance with an embodiment of the invention. The first step of theprocess 140 is to perform wafer level testing (step 150) of devicesfabricated on the wafer. This step is performed in accordance with priorart techniques. The next processing step is to designate faulty dice(step 152). FIG. 17 illustrates a wafer 170 with designated faulty dice172 identified in accordance with step 152. In accordance with prior arttechniques, the wafer 170 would be cut to form individual dice at thispoint. In contrast, the present invention groups functional dice (step154) at this point. The result of this process is shown in FIG. 18,which illustrates the wafer 170 including grouped functional dice 180A,180B, 180C, and 180D. In the present example, this process results inindividual dice 182A, 182B, and 182C.

Interconnect is then applied to the grouped, functional dice (step 156).FIG. 19 illustrates interconnect 54 attached to the grouped, functionaldice 180. At this point, scribe lines can be defined within scribe lanesthat will be cut (step 158).

The next processing step shown in FIG. 16 is to cut the wafer (step160). After the wafer is cut, grouped functional dice are packaged (step162). Each packaged device is then tested (step 164). If an individualdie is identified as non-functional at this point, a bypass is appliedfor the non-functional devices (step 166). This bypass operation is ofthe type described in connection with FIGS. 13-14. Observe that thebypass operation may be used to disable faulty devices identified duringwafer level testing. Alternately, wafer level testing may be avoidedaltogether and faulty devices may be identified and isolated once theyare in a package.

There are a number of inventive features associated with the process ofFIG. 16. First, observe that the grouping of functional dice is notperformed until after faulty dice are identified. This allowsnon-defective sub-circuits to be grouped according to locations ofdefective sub-circuits. Next, note that the interconnect is applied toselected devices after appropriate grouping. Further, the process ofFIG. 16 flexibly defines scribe lines after the grouping of devices. Theprocess of FIG. 16 further includes the step of exploiting a bypassfeature for non-functional devices. This step is advantageouslyperformed after the semiconductor is placed within its package.

The advantages of the invention are more fully appreciated withreference to FIGS. 20A-20C. FIG. 20A illustrates a wafer 40 with a setof semiconductor devices 41A-41F formed thereon. Scribe lanes 39separate individual semiconductor devices 41. An interconnect substrate72 is positioned over the wafer 40 and supports the interconnect channel54. Bond pads or vias 58 are used to establish electrical communicationbetween the interconnect channel 54 and individual semiconductor devices41.

FIG. 20B illustrates a set of semiconductor devices 41A-41D cut from thewafer 40. The figure also illustrates the interconnect channel 54positioned on the interconnect substrate 72. In this embodiment, thesemiconductor devices 41A-41D are positioned on a motherboard 62.Electrical connections are established between the interconnect channel54 and the motherboard 62 via bond wires 190.

FIG. 20C illustrates a set of semiconductor devices 41E-41F cut from thewafer 40. The figure also illustrates the interconnect channel 54positioned on the interconnect substrate 72. Once again, electricalconnections are established between the interconnect channel 54 and themotherboard 62 via bond wires 190.

FIG. 21 is a cross-sectional view of a substrate 50 (e.g., a firstsubstrate) with a set of slave devices 52A-52N embedded therein. Thesignals from the slave devices 52A-52N are routed to a second substrate62 (e.g., a printed circuit board or a motherboard) via an interconnectchannel 54 (e.g., a third substrate or interconnect substrate). Observein FIG. 21 that the interconnect channel 54, for example in the form ofa flexible tape, also operates to route signals between slave devices52A-52N. Thus, the interconnect channel 54 operates as a multidrop busfor a single substrate 50 having a set of slave devices 52A-52N.

The configuration of FIG. 21 stands in sharp contrast to a prior artimplementation shown in FIG. 22. FIG. 22 illustrates a substrate 200Awith a single slave device 202A embedded therein. Signals from the slavedevice 202A are routed to the motherboard 62 via package pins 206A-206Nof the package 204A enclosing the substrate 200A. The motherboard 62must support multiple packages 204A-204N. Each package 204 requires itsown set of package pins 206A-206N for signal routing. Observe that thestructure of FIG. 22 requires signals between slave devices 202 (e.g.,from 202A to 202N) to be routed over the motherboard 62. In contrast,with the system of FIG. 21, these slave-to-slave signals may be routedinternally with the interconnect channel 54, thereby bypassing themotherboard 62. This allows for greater processing speeds. In addition,it can be readily appreciated that the configuration of FIG. 22 requiresa large number of packages, whereas the system of FIG. 21 can utilize asingle package for all of the slave devices 52A-52N formed within thesubstrate 50.

Those skilled in the art will appreciate that various combinations ofthe embodiments of FIGS. 4-13 may be used in accordance with theinvention. That is, various techniques may be used to connect theinterconnect structure to an external package or motherboard, andvarious techniques may be used to connect a package enclosing a set ofslave devices to a motherboard or similar mounting structure.

In each embodiment of the invention, slave devices are combined to forma high density package. For example, the individually packaged slavedevices 32A-32E of FIG. 2 can be substituted with a single package 90,in accordance with the invention.

Those skilled in the art will recognize a number of advantagesassociated with the invention. First, the invention produces highdensity systems. The high density systems reduce signal propagationtime. In addition, the high density systems reduce packaging costs,since a number of devices are positioned in a single package, instead ofeach device having its own package. Further, the structure of theinvention improves thermal performance, since a larger semiconductorsubstrate, which is highly thermally conductive, is available to spreadheat.

The traces forming the interconnect channel can be extremely narrow.This facilitates high density routing. The invention also reduces thenumber of external inputs and outputs since many signals will only berouted internally between semiconductors.

The invention facilitates various design optimizations. For example, iffive slave devices are each implemented as a memory with a smallassociated controller, in many cases a single controller can be used fora set of slave devices. This sharing of resources is efficient, and italso improves manufacturing yield since simplified slave devices areeasier to fabricate.

Note that memory systems typically employ an even number of slavedevices. Grouping an odd number of slave devices allows for redundancyin case one slave device is found to be defective during manufacturingand assembly.

The invention improves performance in master-slave systems, such asmemory systems. The improved performance can be exploited to increasethe information bandwidth of computers and computer subsystems.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. In otherinstances, well known circuits and devices are shown in block diagramform in order to avoid unnecessary distraction from the underlyinginvention. Thus, the foregoing descriptions of specific embodiments ofthe present invention are presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, obviously many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, the therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A method of forming a semiconductor system, saidmethod comprising the steps of: forming a plurality of semiconductordevices in a wafer having a surface wherein each semiconductor device ofsaid plurality of semiconductor devices is designed for independentoperability and is electrically isolated within said wafer from adjacentsemiconductor devices of said plurality of semiconductor devices byscribe lanes, said forming step including the step of forming withineach semiconductor device, a set of input nodes and a set of outputnodes on the surface of said wafer; grouping a set of semiconductordevices that are adjacent to one another on said wafer; and applying aninterconnect channel to said set of semiconductor devices so as toelectrically link input nodes and output nodes of each semiconductordevice within said set of semiconductor devices.
 2. The method of claim1, further comprising the step of prior to said grouping step,identifying faulty semiconductor devices and operable semiconductordevices within said plurality of semiconductor devices.
 3. The method ofclaim 2, wherein said identifying step includes the step of performingwafer level testing.
 4. The method of claim 2, wherein said applyingstep includes the step of depositing metal traces to said set ofsemiconductor devices to form said interconnect channel.
 5. The methodof claim 4, wherein said metal traces each have a controlled impedancebetween 20 Ohms and 100 Ohms.
 6. The method of claim 2, wherein saidapplying step includes the step of applying an interconnect channelformed in an interconnect substrate to said set of semiconductordevices.
 7. The method of claim 6, wherein said applying step includesthe step of selecting an interconnect substrate from the groupconsisting of a thin-film substrate, a flexible tape, and a printedcircuit hoard.
 8. The method of claim 1, further comprising the step ofcutting said wafer within selected scribe lanes to isolate said set ofsemiconductor devices.
 9. The method of claim 8, further comprising thestep of placing said set of semiconductor devices within a package. 10.The method of claim 9, further comprising the step of testing said setof semiconductor devices within said package.
 11. The method of claim10, further comprising the step of disabling an inoperativesemiconductor device of said set of semiconductor devices.
 12. A methodof forming an integrated circuit, said method comprising the steps of:forming, on a semiconductor substrate, a set of semiconductor devicesseparated by scribe lanes; and forming an interconnect channel extendingacross selected scribe lanes to electrically connect at least twosemiconductor devices of said set of semiconductor devices.
 13. Themethod of claim 12, wherein forming the interconnect channel includesforming and patterning metal traces positioned on an interconnectsubstrate.
 14. The method of claim 13, wherein said interconnectsubstrate is polyimide tape.
 15. The method of claim 13, includingconnecting said metal traces to external circuit board traces, saidmetal traces each having an impedance that matches an impedance of eachof said external circuit board traces within plus or minus 30%.
 16. Themethod of claim 13, including connecting each of said metal traces to acorresponding termination resistor, said metal traces each having animpedance that matches an impedance of said corresponding terminationresistor within plus or minus 30%.
 17. The method of claim 12, whereinsaid interconnect channel includes an input end to receive a set ofinput signals and an output end to route a set of output signals. 18.The method of claim 12, wherein each semiconductor device of said set ofsemiconductor devices is a memory device.
 19. The method of claim 12,wherein each semiconductor device of said set of semiconductor deviceswas formed in said semiconductor substrate.
 20. The method of claim 12,wherein each semiconductor device of said set of semiconductor devicesis designed for independent operability.
 21. The method of claim 12,including modifying a flawed semiconductor device of said set ofsemiconductor devices to form a bypass connection so as to disable saidflawed semiconductor device, while allowing the remaining of said set ofsemiconductor devices to operate.
 22. The method of claim 21, whereinsaid bypass connection includes a connection from an input bypass bondpad, to a lead, to an output bypass bond pad.
 23. The method of claim12, wherein said semiconductor substrate has a surface, and eachsemiconductor device of said set of semiconductor devices includes a setof input nodes and a set of output nodes formed on the surface of saidsemiconductor substrate.
 24. The method of claim 23, wherein saidinterconnect channel is positioned on said set of input nodes and saidset of output nodes of said set of semiconductor devices.
 25. The methodof claim 12, including forming said interconnect channel on aninterconnect substrate.
 26. The method of claim 25, wherein saidinterconnect substrate is selected from the group consisting of athin-film substrate, a flexible tape, and a printed circuit board. 27.The method of claim 26, including linking said set of semiconductordevices to said interconnect substrate with bond balls.
 28. The methodof claim 26, including linking said set of semiconductor devices to saidinterconnect substrate with bond balls positioned on said interconnectsubstrate.
 29. The method of claim 12, including forming a signalrepeater on said semiconductor substrate, said interconnect channellinking said signal repeater and said set of semiconductor devices.